The Senza study was a multicentre, randomized, pragmatic, parallel-arm, noninferiority trial comparing high-frequency spinal cord stimulation to traditional tonic stimulation in 198 patients with chronic intractable back and leg pain. Furthermore, 8 of 50 (16%) patients receiving spinal cord stimulation ceased opioids, versus 1 of 44 (2%) with sole medical management. For secondary outcomes, patients receiving spinal cord stimulation experienced improved quality of life and functional capacity, with greater treatment satisfaction. At 12 months, this was achieved in 34% of patients receiving spinal cord stimulation versus 7% of patients who were solely medically managed ( p = 0.005). The primary outcome was 50% or better leg pain relief on 10 cm visual analogue scale score (VAS). The Patients with Failed Back Surgery Syndrome (PROCESS) study, conducted in 2007, was an international, multicentre, randomized trial comparing tonic spinal cord stimulation plus medical management, versus medical management alone in 100 patients with failed back surgery syndrome. 4 Below is a description of 3 of the most influential studies conducted on efficacy of the treatment. In a 2020 systematic review of 15 randomized controlled trials, Hofmeister and colleagues found a robust body of evidence supporting spinal cord stimulation. 8 Wall and Melzack’s gate control theory is the most accepted proposed pain relief mechanism, which asserts that nonpainful inputs close the “nerve-gates” to painful inputs, thereby preventing pain sensations from reaching the brain 2, 7 ( Figure 1). The generators continuously emit low-frequency electrical pulses (tonic stimulation) that mask pain signals travelling up the spinal cord and replace them with nonpainful paresthesias. After this period, patients may resume most physical activities. Patients are asked not to twist, bend or stretch excessively for 6–8 weeks postoperatively. Implantable pulse generators last 5–10 years, depending on rechargeability, and are replaceable. These generators contain a battery and microprocessor (similar to a pacemaker) that are internalized within a subcutaneous pocket either within the abdominal wall or posteriorly in the flank or gluteal region, and programmed transcutaneously while allowing remote control by the physician or patient. Spinal cord stimulation consists of leads placed in the epidural space alongside the dorsal column and then tunnelled subcutaneously to an implantable pulse generator. 3 This difference is likely related, at least in part, to a lack of awareness about spinal cord stimulation and high upfront device costs ($20 000–$30 000). Usage of spinal cord stimulators has increased worldwide, and according to the United States Food and Drug Administration, an estimated 50 000 devices are implanted annually in the US (150 cases/million population However, uptake in Canada has been substantially lower, with 172 implantations performed in Ontario in 2018 (12 cases/million population). 2 The technology has since advanced, and it was a Canadian neurosurgeon who helped demonstrate both the efficacy and cost-effectiveness of spinal cord stimulation in chronic pain treatment. 2, 3, 5 It is based on the principle of electrically stimulating the dorsal column of the spinal cord, to mask pain signals. Neuromodulation, defined as the alteration of nerve activity through targeted stimulus delivery, was first introduced in 1967. When conventional therapies produce unacceptable adverse effects or do not provide sufficient pain relief, spinal cord stimulation (neuromodulation) may offer a rescue option, either alone or in conjunction with other modalities. 1, 2 Consequently, alternatives - including cognitive behavioural therapy, physical rehabilitation, non-opiate pharmacology and integrative therapies - have been developed. 1 Although opioids have been the mainstay of treatment, they have lost favourability owing to crises of addiction, abuse, tolerance and dependence. Increased awareness of and access to spinal cord stimulation therapy may allow more Canadians to benefit from relief of intractable chronic pain and may reduce opioid consumption.Ĭhronic pain affects 1 in 5 Canadians and is associated with considerable socioeconomic burden. Newer spinal cord stimulation technologies are expanding clinical indications such as visceral and ischemic pain, with potential for further improved efficacy. Spinal cord stimulation is safe, efficacious and cost-effective in chronic pain management of neuropathic pain conditions, including failed back surgery syndrome, chronic regional pain syndrome and chronic peripheral neuropathies. Spinal cord stimulation masks pain signals through a transcutaneous implantable electric pulse generator.
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